Blower changes from vent to floor when accelerating - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 09-26-2004, 10:56 PM   #1
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Default Blower changes from vent to floor when accelerating

I have this anoying problem with my 97. When I accelerate the air flow changes from the vent to the floor. The dash control does not change. I assume it is vacuum related. I disconected a vacuum line near the relays that are mounted in the engine compartment. This defaulted to the floor. I don't know what that told me, besides it being vacuum related.

I have changed most of the vacuum hoses and fitting on the engine. But not all of them. I just found a tank under the front right fender that might have a loose fitting.

Any thoughts would be apprecitated.

p.*. I suffer from the chugging and surgging problem, and have apprecitated the discussion on how to resolve this problem.
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Old 09-26-2004, 11:51 PM   #2
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There may be a vacuum leak somewhere, also the vacuum tank may have a leak. The tank is on the engine firewall near the power booster.
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Old 09-27-2004, 11:57 PM   #3
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That seems logical. They tank you refer to, is it the same thing as the "tank" that I have located in the right fender under the battery? This tank has only 1 line going to it.
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Old 09-28-2004, 12:10 AM   #4
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In my signature picture, it'* on the firewall in front of the driver. Between the maxifuse relay center cover and the windshield wiper motor. It'* black, and actually looks like part of the maxifuse relay cover. But it'* actually a vacuum accumulator. You'll see the vacuum lines going to it.
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Old 09-28-2004, 04:32 PM   #5
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Quote:
Originally Posted by string
That seems logical. They tank you refer to, is it the same thing as the "tank" that I have located in the right fender under the battery? This tank has only 1 line going to it.
Um, no, that sounds more like a charcoal canister. The vacuum booster/reservoir that we're pointing you to usually lives on or near the firewall, like WillWren says.

Since your problem only occurs during acceleration, you're losing more than the usual amount of intake manifold vacuum, more than the booster/reservoir can cover for short periods of time. If you haven't got a partial leak in a vacuum line somewhere, you may have a partially-blocked exhaust (e.g. a partially-clogged catalytic convertor), and excess backpressure is killing your intake manifold vacuum.
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Old 09-29-2004, 01:18 PM   #6
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When you mentioned that you changed the "fitting" on the motor, were you talking about a 3-way nipple with a canister (bulge) in the center? That'* a vacuum check valve, if that goes bad you lose you vacuum on acceleration... If you haven't yet tried a new one I found one in the "Help" aisle at Autozone, around $4.
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Old 09-29-2004, 08:14 PM   #7
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I have been kicking around the idea of a plugged cat for some time now.

I am familiar with the vacuum canister on the older bonnies, and can identify it in Willrens photo. On my 97, in that location is an electronic criuse control module. I believe the vacuum canister on mine is under, and I do mean under the battery. Accessible only from under the car on the passenger side.

As far as the "fitting" I replaced, I meant fittings. I have replaced most of the fittings that connect from the hard lines to various components.
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Old 10-31-2004, 10:35 PM   #8
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Fixed!!!

I spent about an hour with a vacuum pump. Started at the vacuum canister and worked my way back to the Y for the line to the dash. There was a small hole in the hard line running under the batery to the vacuum canister.

I spliced the line with the correct size of flexable tubing and have not had an more problem with the changing vents.
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